In modern internal combustion engines, either gasoline (spark ignited) or diesel (compression ignited), fuel typically is provided to the individual cylinders by individual fuel injectors that draw fuel from a common fuel distributor, known in the art as a fuel rail. Each fuel injector is mated to the fuel rail via an injector socket.
A typical injector socket has a cylindrical inner wall or bore that intersects the fuel rail wall to permit fuel to flow from the fuel rail into the socket. A fuel injector includes a cylindrical fuel tube for insertion into the socket and further includes one or more O-rings disposed on the fuel tube for sealing against fuel leakage between the fuel tube and the socket. The O-ring typically is retained on the fuel tube by a retainer mechanism attached to or formed from the outer end of the fuel tube. During manufacture of the fuel injector, the retainer mechanism is typically formed prior to installation of the O-ring onto the fuel tube; thus, the O-ring must pass over the retainer mechanism to complete the assembly. Further, should the injector be serviced later and the O-ring replaced, the replacement O-ring must again be stretched over the retainer mechanism.
In some prior art arrangements, the retainer is a stamped metal part swaged onto the fuel tube or a radially flared end of the fuel tube itself. Either arrangement typically leaves a rough metal edge on the retainer that can inflict damage on the O-ring during assembly, causing a fuel leak during subsequent use of the injector. Further, if the fuel injector is cocked slightly when entering into the socket, the metal retainer edge can inadvertently score the socket wall, which may cause a fuel leak during injector use. Smoothing of the metal retainer is an added manufacturing cost and cannot fully assure that such damages will not occur. Alternatively, the retainer may be overmolded onto the fuel tube with a softer plastic material to prevent scoring of the socket wall. However, this too adds to the manufacturing costs and raises durability issues as well.
In some other prior art arrangements, an annular groove is formed in the outer wall of the fuel tube and a plastic retainer is either overmolded into the groove or is pressed thereinto. An overmolded or pressed retainer in the groove is subject to breakage due to torsional forces acting on the ring because the axial stress vectors are not directly opposed. Either of these forming and assembly process can add significantly to the manufacturing cost of an injector.
What is needed in the art is an inexpensive, reliable O-ring retainer arrangement for retaining an O-ring on the fuel tube of a fuel injector wherein the arrangement cannot damage the bore of an injector socket and wherein the retainer has superior compressive shock resistance.
It is a principal object of the present invention to prevent damage to an O-ring during installation of the O-ring onto a fuel tube of a fuel injector.
It is a further object of the present invention to prevent damage to a fuel injector socket during assembly of a fuel injector into the socket.
It is a still further object of the present invention to prevent compressive strain of an O-ring retaining means during use.